Method of fastening a tissue or a corresponding prosthetic element in an opening provided in a human or animal bone and fastener suitable for the method

ABSTRACT

A graft or prosthetic element suitable, e.g., for replacing a tendon or ligament is fastened in a bone tunnel or blind opening with the aid of a fastener. In a first step, the graft or prosthetic element is press-fitted in the tunnel or opening by forcing the fastener into the opening or by positioning the fastener in the opening and then expanding it, wherein the fastener is in contact with the graft or prosthetic element and with the bone wall of the tunnel or blind opening. In a second step, the fastener is anchored in the bone wall of the tunnel or blind opening with the aid of a liquefiable material which is liquefied in the vicinity of the bone wall where it is in contact with the fastener and by making the liquefied material penetrate into the bone wall.

FIELD OF THE INVENTION

The invention belongs to the field of orthopedic surgery and concerns amethod of fastening a tissue or a corresponding prosthetic element in anopening provided in a human or animal bone. The invention furtherconcerns a fastener being suitable for the method.

The tissue or prosthetic element to be fastened, with the aid of methodand fastener according to the invention, in an opening provided in ahuman or animal bone has the function of a soft tissue and is inparticular a ligament or tendon graft (e.g. bone-tendon-bone graft ortendon graft with at least one stitched end) or an artificial ligamentor tendon substitute or partial substitute for replacing orstrengthening a ruptured or otherwise defect ligament or tendon, butthis tissue may also be a natural ligament or tendon to be re-attachedto a bone from which it has been detached by injury or surgery. Thismeans that the tissue or corresponding prosthetic element is inparticular a soft tissue, a soft tissue graft or a soft tissuesubstitute or partial substitute, which may however, where it is to befastened to the bone, comprise a piece of bone tissue or of acorresponding replacement material, which is attached to the soft tissueand which in this case is fastened in the opening. One or both ends ofthe tissue or corresponding prosthetic element to be fastened may bestrengthened or in particular in the case of a graft comprising aplurality of strands may be held together by stitching, wherein sutureends extending away from the graft may also used for positioning andtensioning the graft.

The opening provided in the bone for the fastening is in a per se knownmanner a tunnel leading through the bone or a blind opening extendinginto the bone from a bone surface and comprising within the bone aclosed end. This opening is preferably provided by drilling but can alsobe provided by e.g. punching (e.g. ultrasonic punching), i.e. thisopening will often have a circular or non-circular cross sectionremaining constant over most of the depth of the opening, but this isnot a condition for the invention. The opening may also have a pluralityof sections with differing cross sections, may have a conical form, ormay be undercut. (e.g. made by milling which allows to produce threedimensional geometries within the opening).

One exemplary application of the method and fastener according to theinvention is the replacement of a ruptured anterior cruciate ligament(ACL) in a human knee by a graft which is fastened on the one hand in anopening extending from the tibia plateau and on the other hand in anopening extending from the articular surface of the distal femur end.

BACKGROUND OF THE INVENTION

According to the state of the art, a ruptured anterior cruciate ligamentis replaced e.g. by a graft, such as e.g. a patellar tendon graftcomprising two terminal bone blocks, a hamstring tendon graft(semitendinosus tendon, possibly combined with gracilis tendon), usuallybeing folded and stitched in the end region, i.e. not comprisingterminal bone blocks, or a quadriceps tendon graft, which is usuallyharvested with one terminal bone block. The named grafts are usuallyautografts but may also be donor grafts (allografts). Donor grafts mayalso be made of achilles tendons. It is further proposed to usesynthetic ribbons (herein called “artificial grafts”) and suitablytreated tendon material of slaughtered animals (xenografts), e.g. pigs.The named autografts and allografts may furthermore be reinforced withsynthetic material and be combined with bone grafts or synthetic bonesubstitutes

End regions of all the named grafts (autografts, allografts, xenograftsand artificial grafts) need to be fastened in tibia and femur for whichpurpose a tunnel or a blind bore is provided in either one of the twobones. The blind bore originates from the articular surface and endsinside the bone. The tunnel has a first mouth situated in the articularsurface and a second mouth which is not situated in the articularsurface, wherein the first mouth and adjoining tunnel portion may have alarger cross section than the second mouth and adjoining tunnel portion.For fastening the graft in the provided opening a plurality of fastenertypes is known.

A tunnel allows fastening at the inner bone wall of the tunnel (innerfixation) and/or in the vicinity of the second tunnel mouth (outerfixation), a blind opening allows inner fixation only. According to thestate of the art inner fixation in a bone opening is effected e.g. withthe aid of an interference screw, which is screwed into the opening whenthe graft is positioned therein; with the aid of a non-threaded,mechanically expandable or non-expandable press-fit element, which isforced without rotation into the opening when the graft is positionedtherein or together with the graft; or with the aid of a cross pin whichis implanted at an angle to the axis of the opening and engages e.g. afolded end of the graft or a suture loop attached to the graft end. Inblind openings inner fixation can also be effected with the aid of abone screw comprising a head section to which the graft is fixed (hookscrew) and which is screwed into the bottom of the blind opening. Innerfixation in a tunnel is usually completed by closing the second tunnelmouth with a bone plug or similar prosthetic element. Variuos devicesand methods for inner fixation are described e.g. in the publicationsU.S. Pat. Nos. 5,454,811 and 6,099,530 (both to Smith &Nephew),EP-0317406 (Laboureau), or US-2009/222090 (Mayr).

Outer fixation (fixation in the area of a second tunnel mouth notsituated in the articular surface) according to the state of the art iseffected e.g. with the aid of a button through which the folded graft ora suture loop attached to a graft end is threaded and which is largerthan the cross section of the second mouth, or with the aid of a bonescrew or similar anchor element which holds the graft or suture endsattached thereto and is screwed or impacted into the bone in thevicinity of the second tunnel mouth. Such outer fixation is alsoproposed for reinforcing an inner fixation inside the tunnel.

For an inner fixation in a bone tunnel or blind opening with the aid ofa fastener such as an interference screw or a press-fit element, thegraft or an end portion of the graft respectively is pressed against oneside of the opening, while the fastener occupies the other side of theopening. This so called extra-graft fixation is mainly used forone-strand grafts and for grafts comprising a terminal bone block butmay also be used for multi-strand grafts. For grafts comprising twostrands by e.g. being folded over, the fastener may also be positionedbetween the two strands separating them from each other, wherein theseparated strands are pressed against opposite walls of the boneopening. Such fixation is called intra-graft fixation. Intra-graftfixation is also used for grafts of four or more than four strands,wherein the strands of the graft are pressed against the wall of thebone opening, preferably substantially regularly spaced around thefastener and wherein, between neighboring strands the fastener may ormay not be in contact with the bone wall of the opening. Intra-graftfixation is proposed in particular for the graft end at which the strandor strands are folded.

The publication WO 2006/023661 (Scandious Biomedical) discloses a largenumber of known methods of ACL-fixation, in particular intra-graftfixation with the aid of press-fit fasteners which are additionallysecured in the bone tunnel or blind bore.

The quality of most inner graft fixations is in particular dependent onthe interface between the graft and the fastener on the one hand andbetween the graft and the wall of the opening on the other hand, but inmost cases it is also dependent on the interface between the fastenerand the wall of the opening, wherein good primary stability is desiredat all the named interfaces and good long-term stability in particularat the interface between graft and bone tissue (good integration of thegraft in the natural tissue by natural tissue growth after the fixationoperation). The fixation quality is found to be further depending on thefixation location in the opening, wherein fixation as close to thearticular surface seems to be advantageous. For shorteningconvalescence, good primary stability is desired, for good long-termstability, bone growth in the opening. For allowing a maximum of bonegrowth in the opening, bioresorbable interference screws and press-fitelements are proposed. Furthermore, it is important that the fastenercauses as little damage as possible to the graft neither when beingimplanted nor later on, and that the graft causes as little widening orother damage as possible to the mouth of the opening, in particular forthe case in which this mouth is situated in an articular surface.

The most common failures of known soft tissue fixation methods arecaused by graft or tissue damage through the threads of interferencescrews which can lead to graft or tissue rupture, graft or tissueslippage due to relaxation of a corresponding press fit, or fastenermigration on first loading e.g. due to compression of bone tissue inresponse to anchoring elements such as e.g. barbs, which may lead toloss of tension in the graft or soft tissue.

Known fixation of ligaments other than the anterior cruciate ligament(graft or prosthetic element, or re-attachment of natural ligament), oftendons (graft or prosthetic element, or re-attachment of naturaltendon), or of other mainly soft tissues (graft or prosthetic element,or repair) in a bone opening provided for the fixation, with the aid ofa fastener are based on the same principles as the above shortlydescribed known fixations used for fastening ACL-grafts in openingsprovided in tibia and femur. Such fixations are e.g. used in surgicalprocedures regarding the human foot or ankle, such as e.g. lateral anklereconstruction, FDL tendon transfer (flexor digitorum longus), FHLtendon transfer (flexor hallucius longus), or flexor to tendon transfer(second toe); surgical procedures regarding the human hand such as e.g.ligament reconstruction tendon interposition, scapholunate ligamentreconstruction, collateral ligament reconstruction, or UCL repair (ulnarcollateral ligament) of the thumb (also known as “gamekeeper's thumb”);surgical procedures regarding the human elbow such as e.g. UCL repair(ulnar collateral ligament), or distal biceps tendon repair; or surgicalprocedures regarding the human shoulder such as e.g. proximal bicepstendon repair. A further example is the repair of torn or damagedcranial cruciate ligaments (CCL) in stifle joints of dogs in particularbut also of e.g. cats. The CCL is the most commonly damaged stifleligament in dogs and the named repair is e.g. carried out using nylonbands which are passed around the fabella bone in the back of the femurand are fixed in a bore provided in the front part of the tibia. Thesame as known fixation methods, the fixation according to the inventionis suitable for all the named applications.

SUMMARY OF THE INVENTION

The object of the invention is to create a further method and fastenerfor fastening tissue or a corresponding artificial element (to beunderstood as: fastening of autograft, allograft, xenograft, orcorresponding prosthetic element substituting natural tissue, or repairof natural tissue fixation) inside an opening (“inner fixation” inside atunnel or inside a blind opening) provided in a human or animal bone,wherein method and fastener according to the invention are to be simpleand suitable for a large number of different types of tissues andprosthetic elements as well as for a large number of different types ofapplications and operation techniques (in particular arthroscopic typesurgery) without the necessity of substantial adaptation. In particular,method and fasteners according to the invention are to be suitablewithout substantial adaptation to be used in anterior cruciate ligamentreplacement surgery using any type of graft (one-strand, two-strand ormulti-strand autograft, allograft, xenograft, or artificial graft, withor without terminal bone block or corresponding artificial graft partand with or without stitched end portions).

The named objects are achieved by method and fastener as defined in theappended claims.

The fixation produced with method and fastener according to theinvention is an “inner” fixation (fastener is positioned in the tunnelor blind opening and fastens the tissue to the inside wall of theopening) and is basically a combination of press-fitting the graft inthe opening using a fastener which clamps the graft against a firstportion of the wall of the opening and subsequent anchoring of thefastener in a second portion of the wall of the opening by establishinga positive-fit connection between the anchor and this second wallportion. This means that the press-fit and the positive-fit are effectedafter each other, locally separated from each other and fullyindependent of each other.

The press-fit connection is achieved in a per se known manner using afastener dimensioned for being forced into the opening (correspondingdimensioning of fastener and opening) or using a fastener which ispositioned in the opening and is then expanded, wherein forcing orpositioning the fastener in the opening is carried out either when thetissue or artificial element to be fastened is already positioned in theopening or together therewith and wherein forcing or positioning withoutrotation of the fastener is preferred but not a necessity. The tissue orartificial element to be fastened is arranged in the opening such thatit does not cover the whole wall of the opening and the fastener isoriented such that a fastener portion equipped for achieving thepositive-fit connection is facing a wall portion not covered by thetissue.

The positive-fit connection is achieved with the aid of an anchoringelement comprising a material capable of being liquefied by applicationof energy (preferably a material having thermoplastic properties), byliquefying the material in situ such that the liquefied material iscapable to penetrate preferably the trabecular structure of the bonetissue of the wall of the opening, where on re-solidification itconstitutes an anchorage in the form of a positive-fit connection. Theanchoring element is positioned relative to the fastener before or afterpress-fitting the fastener in the opening and is then advanced relativeto the fastener using an anchoring tool which simultaneously transmitsthe energy needed for the liquefaction to the anchoring element or tothe fastener. For preventing possible weakening of the press-fitestablished before the anchoring process, the force used for advancingthe anchoring element needs to be small compared with the force used forestablishing the press-fit and/or needs to be counteracted such that itdoes not urge the fastener in a direction in which it was forced intothe opening.

It is possible also to firstly treat the bone wall of the opening with afirst portion of liquefiable material such that the trabecular structureof this wall is penetrated and therewith re-enforced by the liquefiablematerial and only then press-fitting fastener and graft in the openingand carrying out the above described anchoring step, wherein a secondportion of liquefiable material is welded to the pretreated wall of theopening. This two step anchoring procedure results in a samepositive-fit connection as the above described single step procedure ifthe first and second portions of liquefiable material comprise the sameliquefiable material. However, the first and second portions maycomprise different liquefiable materials under the condition that thetwo materials are weldable to each other under the conditions of theanchoring step. For achieving a good anchorage it may be advantageous oreven necessary to provide, in addition to or in place of pores orcavities of the trabecular network of the bone tissue, further cavitiesin the bone wall of the opening to be filled with the liquefied material(e.g. undercut form of opening in the bone tissue).

For the separate fastener functions of pressing (press-fit connectionwith tissue to be fastened) and anchoring (positive-fit connection withbone tissue of the wall of the opening), the fastener according to theinvention comprises separate surface portions equipped either for thepressing function or for the anchoring function. The surface portionsequipped for the pressing function may, in a per se known manner, have aflat or concave form (shallow groove) and be rough or otherwisestructured for retention of the tissue to be fastened, but may also lackany specific form or structure. The surface portions equipped for theanchoring function comprise means for guiding liquefiable materialcomprised by the anchoring element from the fastener inside or theproximal fastener face to these surfaces portions and they may furthercomprise reaming or cutting edges, threads, barbs or other per se knownstructures for additional support of the fastener in the bone wall ofthe opening.

In a preferred fastener embodiment the surface portions equipped foreither pressing or anchoring constitute sectors of a circumferentialsurface, wherein a fastener suitable for extra-graft fixation comprisesone pressing sector and one anchoring sector and a fastener suitable forintra-graft fixation comprises a plurality of such sector pairs.Alternatively, the fastener surface portions equipped for eitherpressing or anchoring may be arranged beside each other along a fasteneraxis, or such alternatively arranged surface portions may be provided onthe fastener in addition to the above named surface sectors.

The fastener according to the invention has e.g. the general form of acylinder, frustum or cone (continually tapering or stepped), preferablybut not necessarily with substantially circular cross sections, i.e. issuitable for being fitted into an opening of a substantially circularcross section (cylindrical or tapering continually or in steps), but itmay also have another form such as e.g. a parallelepiped or wedge. Afastener according to the invention having the form of a substantiallycircular cylinder, frustum or cone may comprise in addition to the abovenamed means for guiding the liquefiable material and possibly the meansfor accommodating the graft, a thread extending around the wholefastener circumference or around only part thereof.

The method according to the invention comprises basically four steps:

-   -   (a) providing a fastener and at least one anchoring element        comprising a liquefiable material and providing an opening in a        bone (e.g. by antegrade or retrograde drilling or by punching),        wherein fastener and opening are adapted to each other and to        the graft (understood to include natural tissue and a        corresponding artificial element) to be fastened,    -   (b) press-fitting the graft in the opening, wherein the graft is        not to cover all of the inner wall of the opening, the        press-fitting being carried out by forcing (or positioning and        expanding) the fastener into the opening after positioning the        graft or together with the graft, and    -   (c) anchoring the fastener in the bone tissue of the wall of the        opening by positioning the at least one anchoring element        relative to the fastener and by transferring energy to the        liquefiable material comprised by the anchoring element and        simultaneously advancing the anchoring element relative to the        fastener and therewith liquefying at least part of the anchoring        element and making it to penetrate into the wall of the opening        (or to be welded to the pretreated wall of the opening), where        this wall is not covered by the graft, and    -   (d) letting the liquefied material re-solidify in the wall of        the opening.

The main advantages of the fixation according to the invention is animprovement of the primary stability of the fixation as compared withknown press-fit fasteners as e.g. described by H. O. Mayr et. al. in“Axial load in case of press-fit fixation of ACL graft—a fundamentalstudy” (Z Orthop Ihre Grenzgeb, 143(5): 556-60 (2005)) and“Beta-tricalcium plugs for press-fit fixation in ACL reconstruction—amechanical analysis in bovine bone” (Knee 14(3): 239-44 (2007)).Compared with the known fixation using an interference screw, thefixation according to the invention is possible with substantiallyreduced danger of mechanically damaging the graft to be fastened and issubstantially less dependent on the mechanical properties of the bonetissue in which the opening is provided (allowing fixation in e.g. bonetissue weakend by osteoporosis), because the liquefiable material isadditionally able to strengthen this bone tissue. Further compared withthe interference screw fixation, the fixation according to the inventionpreferably uses a fastener without thread and therefore of a smallerdiameter, which allows a plurality of fasteners to be implanted closertogether. This means that e.g. an ACL graft can be fixed in more thanone opening resulting in a fixation of a wider footprint and thereforecloser resembling the natural ACL-fixation.

Furthermore, the fixation according to the invention can be carried outwithout putting a critical thermal load on the graft to be fastened andis therefore suitable for such graft which is not only mechanicallysensitive but also thermally.

As mentioned already further above, the anchoring technique applied inthe method according to the invention is based on in situ liquefactionof a liquefiable material, in particular of a material havingthermoplastic properties. Such anchoring techniques and fasteningdevices being suitable for such anchoring techniques are disclosed e.g.in the publications U.S. Pat. Nos. 7,335,205, 7,008,226, US2006/0105295, US-2009/131947, WO-2009/132472, WO-2008/034276,WO-2010/127462, and WO-2010/045751, as well as in the U.S. provisionalapplication 61/259,383, which is not published yet. The entiredisclosure of all the named publications and applications is enclosedherein by reference.

The main features of the named implantation techniques is the in situliquefaction of a liquefiable material, penetration of the liquefiedmaterial into a hard tissue surface (trabecular structure and/orsuitable structures or cavities provided in the hard tissue surface) andre-solidification of the liquefiable material in the hard tissuesurface. Therein, the liquefiable material is preferably a materialhaving thermoplastic properties, and being able, in its solid state, totransmit energy and, in its liquefied state, to penetrate a trabecularor similar porous structure. Suitable liquefaction connected with anacceptable thermal loading of the tissue is achievable by usingmaterials with thermoplastic properties preferably having a modulus ofelasticity of at least 0.5 GPa and a melting temperature of up to about350° C. and by liquefying only a necessary minimum amount of thematerial. The energy applied for such liquefaction is preferablymechanical vibration energy of a frequency preferably in the range ofbetween 2 and 200 kHz (preferably ultrasonic vibration with a frequencypreferably between 15 and 30 kHz, even more preferably between 20 and 25kHz), wherein the liquefiable material and possibly other portions ofthe fastener or anchoring element transmit the vibration, preferablywith very little damping to localities where the liquefiable materiale.g. vibrates against a counter element thereby causing friction andtherewith liquefaction.

Instead of using vibrational energy for creating the local thermalenergy needed for the liquefaction of the material with thermoplasticproperties, it is possible also to exploit other energy types, inparticular rotational energy turned into friction heat in substantiallythe same manner as the vibrational energy, or electromagnetic radiation(in particular laser light in the visible or infrared frequency range),which radiation is preferably guided through the material withthermoplastic properties and locally absorbed by an absorber beingcontained in the material with thermoplastic properties or beingarranged adjacent to this material. Electric energy can also be used.

Suitable liquefiable materials for the anchoring element used in thefixation method according to the invention are thermoplastic polymers,e.g.: resorbable polymers such as polymers based on lactic and/orglycolic acid (PLA, PLLA, PGA, PLGA etc.) or polyhydroxy alkanoates(PHA), polycaprolactone (PCL), polysaccharides, polydioxanes (PD)polyanhydrides, polypeptides or corresponding copolymers or compositematerials containing the named polymers as a component; ornon-resorbable polymers such as polyolefines (e.g. polyethylene),polyacrylates, polymetacrylates, polycarbonates, polyamides, polyester,polyurethanes, polysulfones, polyarylketones, polyimides,polyphenylsulfides or liquid crystal polymers (LCPs), polyacetales,halogenated polymers, in particular halogenated polyolefines,polyphenylensulfides, polysulfones, polyethers or equivalent copolymersor composite materials containing the named polymers as a component.

Specific embodiments of degradable materials are Polylactides like LR706PLDLLA 70/30, R208 PLDLA 50/50, L210S, and PLLA 100% L, all byBohringer. A list of suitable degradable polymer materials can also befound in: Erich Wintermantel und Suk-Woo Haa, “Medizinaltechnik mitbiokompatiblen Materialien und Verfahren”, 3. Auflage, Springer, Berlin2002 (in the following referred to as “Wintermantel”), page 200; forinformation on PGA and PLA see pages 202 ff, on PCL see page 207, onPHB/PHV copolymers page 206; on polydioxanone PDS page 209. Discussionof a further bioresorbable material can for example be found in C ABailey et al., J Hand Surg [Br] 2006 April; 31(2):208-12.

Specific embodiments of non-degradable materials are: Polyetherketone(PEEK Optima, Grades 450 and 150, Invibio Ltd), Polyetherimide,Polyamide 12, Polyamide 11, Polyamide 6, Polyamide 66, Polycarbonate,Polymethylmethacrylate, Polyoxymethylene, Polycarbonateurethane (inparticular Bionate by DSM, in particular type 65D and 75D). An overviewtable of polymers and applications is listed in Wintermantel, page 150;specific examples can be found in Wintermantel page 161 ff. (PE,Hostalen Gur 812, Höchst AG), pages 164 ff. (PET) 169ff. (PA, namely PA6 and PA 66), 171 ff. (PTFE), 173 ff. (PMMA), 180 (PUR, see table), 186ff (PEEK), 189 ff. (PSU), 191 ff (POM—Polyacetal, tradenames Delrin,Tenac, has also been used in endoprostheses by Protec).

The liquefiable material having thermoplastic properties may containforeign phases or compounds serving further functions. In particular,the thermoplastic material may be strengthened by admixed fibers orwhiskers (e.g. of calcium phosphate ceramics or glasses) and suchrepresent a composite material. The thermoplastic material may furthercontain components which expand or dissolve (create pores) in situ (e.g.polyesters, polysaccharides, hydrogels, sodium phosphates), compoundswhich render the fusion device opaque and therewith visible for X-ray,or compounds to be released in situ and having a therapeutic effect,e.g. promotion of healing and regeneration (e.g. growth factors,antibiotics, inflammation inhibitors or buffers such as sodium phosphateor calcium carbonate against adverse effects of acidic decomposition).If the thermoplastic material is resorbable, release of such compoundsis delayed. If the device is to be anchored not with the aid ofvibration energy but with the aid of electromagnetic radiation, theliquefiable material having thermoplastic properties may locally containcompounds (particlulate or molecular) which are capable of absorbingsuch radiation of a specific frequency range (in particular of thevisible or infrared frequency range), e.g. calcium phosphates, calciumcarbonates, sodium phosphates, titanium oxide, mica, saturated fattyacids, polysaccharides, glucose or mixtures thereof.

Fillers used may include degradable, osseostimulative fillers to be usedin degradable polymers, including: β-Tricalciumphosphate (TCP),Hydroxyapatite (HA, <90% crystallinity; or mixtures of TCP, HA, DHCP,Bioglasses (see Wintermantel). Osseo-integration stimulating fillersthat are only partially or hardly degradable, for non degradablepolymers include: Bioglasses, Hydroxyapatite (>90% cristallinity),HAPEX®, see S M Rea et al., J Mater Sci Mater Med. 2004 September;15(9):997-1005; for hydroxyapatite see also L. Fang et al., Biomaterials2006 July; 27(20):3701-7, M. Huang et al., J Mater Sci Mater Med 2003July; 14(7):655-60, and W. Bonfield and E. Tanner, Materials World 1997January; 5 no. 1:18-20. Embodiments of bioactive fillers and theirdiscussion can for example be found in X. Huang and X. Miao, J BiomaterApp. 2007 April; 21(4):351-74), J A Juhasz et al. Biomaterials, 2004March; 25(6):949-55. Particulate filler types include: coarse type: 5-20μm (contents, preferentially 10-25% by volume), sub-micron (nanofillersas from precipitation, preferentially plate like aspect ratio >10, 10-50nm, contents 0.5 to 5% by volume). Experiments show that liquefactionwith the aid of ultrasonic vibration energy allows filling thethermoplastic polymer to a relatively high degree without impairing thecapability of the liquefied material to penetrate structures as e.g. thetrabecular structure of viable cancellous bone.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the method and the fastener according to theinvention are described in detail in connection with the appended Figs.,wherein:

FIG. 1 illustrates the invention by showing six consecutive phases of anexemplary extra-graft fixation in a bone tunnel using an exemplaryembodiment of the method according to the invention;

FIG. 2 shows four consecutive phases of an exemplary ACL replacementsurgery using the method as shown in FIG. 1 ;

FIGS. 3 and 4 illustrate two further exemplary applications of graftfixation according to the invention, in a bone tunnel comprising aportion of a reduced diameter (FIG. 3 ) or in a blind bore (FIG. 4 );

FIGS. 5 to 9A/B show further exemplary sets comprising a fastener,anchoring element and an anchoring tool, the sets being suitable for thefixation method according to the invention;

FIGS. 10 to 17 are three-dimensional illustrations or axial sections offurther exemplary fastener embodiments which are suitable for methodssimilar to the ones illustrated in FIGS. 1 and 5 ;

FIGS. 18 to 22 are cross sections through grafts being fixated with themethod according to FIG. 1, 5, 6 or 7 in a bone tunnel or blind borewith the aid of further exemplary fastener embodiments;

FIG. 23 shows an embodiment of the method according to the inventionincluding a pretreatment step in which the wall of the opening istreated with a first portion of liquefiable material before introductionof the fastener;

FIG. 24 shows an embodiment of the method according to the invention,wherein an expandable fastener is used;

FIG. 25 illustrates a further exemplary embodiment of the methodaccording to the invention, the method being suitable for an extra-graftfixation in a bone tunnel or in a blind opening;

FIG. 26 shows a further exemplary embodiment of the method according tothe invention, the method being suitable for an extra-graft fixation ina blind opening;

FIGS. 27 to 33 are cross sections and three dimensional representationsof exemplary fastener embodiments suitable for intra-graft fixationusing a method similar to the one as illustrated in FIG. 1 or 5 ;

FIGS. 34A/B show an exemplary embodiment of a set according to theinvention, the set comprising fastener, anchoring element and anchoringtool and being suitable for an intra-graft fixation using a methodsimilar to the one as illustrated in FIG. 6 or 7 ;

FIGS. 35A/B show an exemplary embodiment of a set according to theinvention, the set comprising fastener, anchoring element and anchoringtool and being suitable for an intra-graft fixation using a methodsimilar to the one as illustrated in FIG. 25 ;

FIG. 36 shows an exemplary footprint of a fixation of a two strand graftaccording to the invention, which footprint is in particular suitablefor the tibial ACL fixation;

FIGS. 37, 38A/B and 39A/B/C show sets of fastener, anchoring element,anchoring tool, and guide tool , wherein the guide tool is suitable notonly for guiding the anchoring tool during the anchoring process, butalso for forcing the fastener into the opening along a guide wire forestablishing the press fit before the anchoring process is started.

Items having the same function and similar items are denominated in allFigs. with the same reference numerals.

DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 shows six consecutive phases (a) to (f) of the fixation(extra-graft fixation) of a soft tissue in a bone tunnel using exemplaryembodiments of method and fastener according to the invention. The softtissue is e.g. a graft 1, which, as seen from phase (a), is positionedto extend through the tunnel 2 and, if applicable, is kept with per seknown measures at a desired tension during the fixation process.However, neither the method nor the fastener need to be different forfastening a prosthetic element or a natural soft tissue in the tunnel,wherein the graft or soft tissue may not extend through the tunnel buthave an end inside the tunnel, and at this end may comprise a terminalbone block. Obviously in the latter case the opening may also be a blindopening, e.g. a blind bore. Furthermore, the graft or soft tissue maycomprise a stitched end portion with suture ends extending therefrom,wherein this end portion is positioned in the tunnel, the suture endportions exiting through the second tunnel mouth and being used e.g. fortensioning the graft or soft tissue (see also FIG. 3 ).

The fastener 3 is adapted in cross section for being capable ofpress-fitting the graft 1 in the tunnel 2. The fastener 3 comprises aninner cavity 4, which is e.g. substantially cylindrical, which extendsfrom the proximal fastener face towards the distal fastener end, andwhich is connected by a passage 5 or a plurality of passages to ananchoring sector of the circumferential fastener surface, i.e. to oneonly side of the fastener 3. The passage 5 may have the form of one or aplurality of e.g. slot-shaped, round or polygonal fenestrations or of anotherwise perforated region (e.g. material with an open porosity, e.g.trabecular or sintered metal or ceramic). The anchoring element 6 ise.g. a pin-shaped item of a material having thermoplastic propertieswhich material is suitable to be liquefied in the above describedmanner, the anchoring element fitting into the inner cavity 4 to reachat least into the region of the passage 5.

The fixation process is preferably carried out as follows: The graft 1positioned through the tunnel 2 as shown in phase (a) is impactedagainst one side of the tunnel wall by introducing a dilator 10 betweenthe graft 1 and the opposite side of the tunnel wall as shown in phase(b), wherein a one-sided tapering dilator 10 as illustrated and usedwith the tapering side facing the graft 1 proves the most effective.This impaction compresses the graft 1 or, if applicable, the terminalbone block thereof. In phase (c) the dilator 10 is removed and thefastener 3 is forced (force F.1) into the space between the graft 1 andthe tunnel wall which space has been prepared in the impaction step.Therein the passage 5 of the fastener 3 faces towards the tunnel wallopposite the graft 1 and the positioned fastener 3 is to press-fit thegraft against the tunnel wall. For forcing the fastener 5 into thetunnel, e.g. a push rod 11 reaching into the inner fastener cavity 4 isused. Instead of using the illustrated push rod 11 for forcing thefastener into the tunnel, a ram tool acting on the proximal fastenerface may also be used. In phase (d) the push rod 11 is removed and areamer 12 is introduced into the inner fastener cavity 4, its angleddistal tip directed to reach through the passage 5. The reamer 12 isreciprocated for reaming the tunnel wall outside the passage 5. In phase(e) the reamer 12 is removed and the anchoring element 6 is introducedin the inner cavity 4 and an anchoring tool 13 is placed on the proximalface of the anchoring element 6 or fixed thereto. Therein it isadvantageous to also position a guide tool 14, this guide tool beingequipped for guiding the anchoring tool 13 and possibly the anchoringelement 6 for being able to be advanced exactly coaxially in the innercavity 4. The anchoring tool 13 serves for producing the anchorage ofthe fastener through the anchoring element in the tunnel wall, i.e. fortransmitting to the anchoring element 6 energy, e.g. ultrasonicvibration, needed for liquefaction of the liquefiable material and aforce F.2 for advancing the anchoring element 6 towards the distalfastener end, such that the material of the anchoring element 6 isliquefied and, in a liquid state is made to flow through the passage 5into the bone tissue of the tunnel wall, where on re-solidification itconstitutes an anchorage 15 of the fastener 3 in the bone tissue asshown in phase (f).

Obviously, in the method as illustrated in FIG. 1 , establishment of thepress-fit (phase (c)) and establishment of the anchorage (phase (e)) arecarried out after each other and independent from each other, whereinforce F.2, which is applied to the anchoring element for the advancementthereof in the anchoring step (phase (e)) is counteracted by thefastener 3 and has the same direction as force F.1 which is needed forestablishing the press-fit (phase (c)), i.e. it has no component in adirection opposite force F.1 and therefore cannot in any way weaken thepress-fit of the graft or soft tissue through the fastener.

Depending on the cross section of the graft 1 in a non-impacted state,the step of impaction (phase (b)) can be omitted. Use of a taperingfastener or tapering distal fastener end may also render the impactionstep unnecessary. Depending on the density of the bone tissue of thetunnel wall and on the desired strength of the anchorage, the step ofreaming (phase (d)) may be omitted. Reaming is advisable for very densebone tissue. If the reaming step is carried out, the anchorage achievedin step (e) will be deeper and will reach bone tissue which has not beencompacted by the press fitting. However, a similar effect may beachieved by equipping the fastener with an axial groove extending fromthe distal fastener end to the outer mouth of passage 5. The guide tool14 may be positioned on the proximal end of the fastener 3 before thereaming step or even before establishing the press fit, wherein in thelatter case, the guide tool is used for forcing the fastener 3 into theopening instead of the push rod 11. Depending on the stroke ofadvancement of the anchoring element necessary for achieving the desiredanchorage (phase (e)) and on the guidability of the anchoring tool 13,use of a guide tool 14 may be omitted.

It may be advantageous to use a guide wire for introducing the dilator10 and/or the fastener 3 into the bone opening which necessitates in aper se known manner an axial channel or bore (centric or ex-centric) inthe dilator 10 and/or the fastener 3. Experiments show that it isadvantageous to provide the axial bore in the dilator 10 and/or fastener3 as close as possible to the circumferential surface of the side whichis to be facing towards the wall of the opening. Instead of the bore itis possible also to provide a groove (preferably undercut) along thecircumferential surface of the dilator and/or the fastener for guidingthese along the guide wire.

FIG. 1 shows the fastener introduced in the bone opening 2 with itsproximal face being flush with the bone surface. This, of course, is nota condition of the method according to the invention. Without alterationto the fastener and the method it is possible also to introduce thefastener further into the bone, such that the proximal fastener end isburied in the bone, or less far, such that the proximal fastener endprotrudes from the bone.

As already mentioned, the anchoring tool 13 is e.g. a vibrating tool(e.g. sonotrode connected to an ultrasonic transducer being e.g. part ofan ultrasonic device such as an ultrasonic hand piece), which transmitsultrasonic vibration to the anchoring element 6 and is simultaneouslypressed against the proximal face thereof or is rigidly fixed theretoand pressed against the closed distal end of the fastener 3 togetherwith the anchoring element. In such a case it is advantageous to provideeither on the anchoring element 6 or inside the inner cavity 4 energydirectors (protruding points or edges) where liquefaction is desired.Such energy director for the fastener 3 and anchoring element 6 in theillustrated case is constituted by the tapering distal end of theanchoring element 6. Alternative embodiments of such energy directorsare e.g. edges or points protruding into the inner cavity from the rimof the inner mouth of passage 5. Further embodiments of such energydirectors are disclosed in the provisional U.S. application No.61/259,383 (not published yet), whose disclosure in its entirety isenclosed herein by reference.

The anchoring tool 13 may also be equipped for transmitting rotationalenergy to the anchoring element being rigidly fixed thereto, wherein theheat required for liquefaction of the anchoring element material is insuch a case produced by friction between the distal face of the rotatinganchoring element and the non-rotating inner fastener surface.Alternatively, the anchoring tool 13 may be equipped for transferringelectromagnetic energy (preferably in the visible or infrared frequencyrange) or electric energy to the anchoring element 6 or to the fastener3, wherein either the anchoring element 6 or fastener regions in thevicinity of the anchoring element need to be equipped for transformingthe transmitted energy into thermal energy by e.g. comprising lightabsorbing means or electric resistance means.

If the fastener 3 according to FIG. 1 is used for extra-graft fixationin a blind opening, it may be desirable to anchor it in addition to theanchorage in the circumferential wall of the opening also in the bottomwall of the opening or exclusively in the bottom wall of the opening(see also FIG. 26 ). In such a case, the fastener needs to be introducedinto the blind bore such that it substantially touches or at least comesnear the bottom wall of the opening and it needs to comprise at leastone passage 5 connecting the inner fastener cavity 4 with a distalfastener face, which passage is provided in addition to or in place ofthe lateral passage 5 illustrated in FIG. 1 . Such distal fastenersurface being equipped for the fastener anchorage constitutes a fastenersurface portion being separated from fastener surface portions equippedfor pressing not as a circumferential sector (as above described for thesurface comprising the lateral passage 5) but as an axial portion, asalready mentioned further above.

The fastener 3 is made of a material which may or may not bebiologically resorbable as known for fasteners according to the state ofthe art, which serve the same purpose. If the fastener is not to beresorbable it is e.g. made of a metal (e.g. titanium, titanium alloy,stainless steel), a ceramic material (e.g. aluminum oxide, zirconiumoxide), a calcium phosphate, or of a polymer (e.g. thermoplastic, e.g.PEEK, possibly coated e.g. with an inner coating of titanium and anouter coating of hydroxyapatite). Although it seems advantageous to makethe fastener of a material which is not liquefiable under the conditionsof the anchoring process, experiments show that the fastener may also bemade of a liquefiable material, even of the same material as theliquefiable material of the anchoring element. Good results have e.g.been achieved with fasteners made of titanium, or of polylactic acid(PLA) filled with Hydroxyapatite or calciumphosphates, in particular ofPLLA filled with 60% tricalciumphosphate or PDLLA 70%/30% (70% L and 30%D/L) filled with 30% biphasic calciumphosphate, combined with anchoringelements of PLDLLA 70%/30% (70% L and 30% D/L), as available fromBohringer as LR706.

Particularly in a case in which the graft (or natural soft tissue orcorresponding artificial element) to be fastened is very heat sensitiveit is preferable to use, at least for a fastener region which is to besituated in the vicinity of the graft, a material which has some heatinsulating characteristics. If the graft to be fastened is less heatsensitive (e.g. artificial tissue replacement material) such precautionis not necessary. For such non-heat-sensitive tissue which in additionis sufficiently deformable it is even possible to provide passages 5directed also to the side of the graft, wherein for the anchoringprocess these passages will be closed by the compacted graft and willnot or hardly permit passage of the liquefied material (advantage: nospecific rotational fastener orientation in the opening is needed).

The extra-graft fixation as illustrated in FIG. 1 can e.g. be achievedby providing a tunnel or blind bore of 8 mm diameter, a substantiallycylindrical fastener of 7 mm diameter and a graft having a stitched endportion which passes easily through a bore of 7 mm diameter. Experimentsshow that substantially cylindrical fasteners with a tapering distalend, in particular with a hemispherical end as illustrated in FIG. 1 andwith a circumferential surface of a roughness of not more than 10 μmdepth give a good press-fit and can be introduced with reasonableforces, while fasteners with flat distal ends and/or a greater surfaceroughness seem to necessitate higher introduction forces but do notresult in a better press fit. A stronger press-fit is achieved by usinglonger fasteners.

FIG. 2 shows in a schematic manner four consecutive phases (a) to (d) ofan exemplary surgical procedure for replacing an anterior cruciateligament (ACL) in a human knee, wherein the graft 1 used for thereplacement comprises e.g. two terminal bone blocks and wherein one ofthese terminal bone blocks is fastened in a blind bore 20 in the femoralbone 21 and the other one in a tunnel 22 reaching through the tibialbone 23. The per se known procedure comprises a femoral and a tibialfixation process which can both be carried out using the methodaccording to the invention as e.g. illustrated in FIG. 1 .

In phase (a) the tibial tunnel 22 and the femoral blind bore 20 areprovided and the graft 1 is positioned for the fixation processes. Inphase (b) the femoral fastener 3.1 is press-fitted in the femoral blindbore 20. In phase (c) the femoral fastener 3.1 is anchored in the wallof the femoral blind bore 20 (anchorage 15.1). In phase (d) the tibialfastener 3.2 is press-fitted and anchored (anchorage 15.2) in the tibialtunnel 22.

FIG. 3 shows as mentioned already further above, the fixation of astitched graft end 16 in bone opening 2 using a fixation method similarto the one illustrated in FIG. 1 . The bone opening 2 is a tunnel andcomprises a portion 2.1 of a larger cross section and a portion 2.2 of asmaller cross section, wherein the stitched graft end 16 and thefastener 3 are arranged in the tunnel portion 2.1 and the suture ends 17extending from the stitched graft end 16 exit through the tunnel portion2.2 and are e.g. used for tensioning the graft before compressing itwith the dilator or introducing the fastener 3. The graft 1 comprisingthe stitched graft end 16 is e.g. a two-strand graft wherein the twostrands are fixed to each other by a series of cross stitches aroundboth lateral sides and made with one suture, the two suture ends 17protruding from the stitched graft end. The graft 1 may also be a fourstrand graft being made by folding in two a two-strand graft with twoends being stitched in the named manner, the four-strand graft thencomprising a fold end without suture ends and a stitched end with fourprotruding suture ends. The step of anchoring the fastener in the wallof the tunnel portion 2.1 is e.g. carried out as above described inconnection with FIG. 1 .

FIG. 4 shows the fixation of a stitched graft end 16 in a bone opening 2being a blind bore, wherein the stitched graft end 16 is fixed to thefastener 3 preferably with the aid of the suture ends 17 protruding fromthe stitched graft end 16. This fixation is established beforeintroduction of the graft end 16 and the fastener 3 in the opening andthe two are introduced together into the opening 2 for establishing thepress-fit.

FIG. 3 shows the graft end 16 and the fastener 3 positioned in the boneopening 2. The step of anchoring the fastener 3 in the wall of theopening is established e.g. in the manner as illustrated in FIG. 1 .

The fixation of a stitched graft end to the fastener 3 can e.g. beachieved, as illustrated in FIG. 4 , by threading a first part of thesuture ends 17 through the inner cavity 4 of the fastener 3, which forthis purpose comprises an open distal end, and a second part of thesuture ends 17 along the circumferential surface of the fastener 3 andproviding a knot or other suitable suture retainer at the proximalfastener face for connecting the two parts of suture ends 17. Thecircumferential fastener surface and/or the inner fastener cavity maycomprise an axially extending groove for accommodation of the sutureends. If the suture is heat sensitive and there is a risk of the sutureto be damaged by the liquefied material inside the inner fastenercavity, it will be advantageous to provide at least one separate tunnelthrough the fastener for the suture (see also FIG. 19 ) It is alsopossible to equip the distal end of the fastener 3 with an eyelet orsimilar retention means to which the suture ends 17 protruding from thestitched graft end 16 can be fixed in a suitable manner before the graftend 16 and the fastener 3 are introduced in the bone opening 2 together.It is also possible of course to fix a non-stitched graft end to thefastener in a suitable manner.

FIGS. 5 to 9A/B show further exemplary embodiments of fasteners 3together with adapted anchoring elements 6 and anchoring tools 13,wherein all the illustrated sets of fastener 3, anchoring element 6 andanchoring tool 13 are suitable for an anchoring step which is slightlydifferent from the anchoring step illustrated in FIG. 1 but which areall suitable for the fixation applications as illustrated in FIGS. 1 to4 . FIGS. 5 to 9 illustrate the anchoring steps for extra-graft fixationbut as discussed further below, their principle is applicable forintra-graft fixation also.

FIG. 5 shows an axial section of a fastener 3 which is press-fitted in abone tunnel 2 for fastening a graft 1 in the bone tunnel. The fastener 3is principally the same as the fastener illustrated in FIG. 1 , but aspassage 5 reaching from the inner cavity 4 to the outer fastener surfacea plurality of openings is provided instead of the one slot-likefenestration according to FIG. 1 . The anchoring element 6 istube-shaped and sits loosely on the foot piece 25 of an extension 26 ofthe anchoring tool 13, which again is preferably a vibration tool. Forthe anchoring process, the extension 26 together with the anchoringelement 6 is introduced into the inner cavity 4 of the fastener 3. Theanchoring tool 13 is then activated and the anchoring element 6 is heldand advanced against the foot piece 25 by applying a corresponding forceF.2 to a counter element 27 acting on the proximal face of the anchoringelement 6. The thermoplastic material comprised by the anchoring element6 is liquefied at the distal face of the anchoring element 6 where it isin contact with the vibrating foot piece 25. By correspondingpositioning of the interface between foot piece 25 and anchoring element6 the liquefied material is made to flow through passage 5 into thetunnel wall, wherein this interface is displaced for subsequentanchoring processes through different passages 5. FIG. 5 shows theset-up during the anchoring process, wherein the anchoring material hasalready been forced through a distal and a middle passage 5, wherein thenamed interface is still positioned at the middle passage, and wherein aproximal passage is still free from the anchoring material.

With the combination of anchoring element 6, anchoring tool 13 andcounter element 27 as shown in FIG. 5 , advancement of the anchoringelement 6 may also be effected by pulling the foot piece 25 towards theproximal face of the fastener 3, while keeping the counter element 27substantially stationary, e.g. pressed against the bone surface. It ispossible also to reverse the functions of anchoring tool and countertool, i.e. to vibrate the counter element 27 and to use the foot piece25 as counter element. Furthermore, for the fastener anchoring asillustrated in FIG. 5 , as already mentioned for the fastener anchoringaccording to FIG. 1 , it is also possible to use energy types other thanvibration energy. Further embodiments and details of the principle ofthe anchoring process as illustrated in FIG. 5 are described in thepublication WO-2009/132472, whose disclosure in its entirety is enclosedherein by reference. In an alternative embodiment of the combination ofanchoring element 6 and anchoring tool 13 as illustrated in FIG. 5 thetube-shaped anchoring element 6 constitutes the consumable element in adispenser-like device and is liquefied at a distal device end in asimilar way as shown in FIG. 5 . Such dispenser devices are described inthe publication WO-2010/127462 whose disclosure in its entirety isenclosed herein by reference.

It is obvious that in the fixation method as illustrated by FIG. 5 theforce F.2 needed for advancing the anchoring element 6 is notcounteracted by the fastener 3. Therefore, this force cannot weaken thepress-fit of the fastener, whatever its direction may be, and it allowsuse of a fastener not having a closed distal end and introducing theanchoring element from either the proximal or distal fastener end.

FIG. 6 is an axial section of a further set of fastener 3, anchoringelement 6 and anchoring tool 13, wherein the fastener 3 is shown in thebone opening 2 before the anchoring step, i.e. press-fitted between thegraft 1 and the opposite wall of the bone opening 2. Other thandescribed above, the fastener 3 does not comprise an inner cavity andpassages connecting the inner cavity to the outer fastener surface (asillustrated in FIGS. 1 to 5 ) but instead, for guiding the liquefiablematerial comprised by the anchoring element 6 from a proximal fastenerface to the anchoring portions of the circumferential fastener surface,the fastener 3 comprises at least one groove 30 which extends from theproximal fastener face towards the distal fastener end and may have aslightly undercut cross section. The anchoring element 6 is adapted tosubstantially fill this cross section and to protrude slightly from itand it is pushed into the groove 30 of the press-fitted fastener 3 fromthe proximal fastener face with the aid of anchoring tool 13. Thereinthe anchoring element 6 is advantageously rigidly attached to the distalend of the anchoring tool 13, such that vibration energy (or other typeof energy) is transmitted substantially loss-free into the anchoringelement and liquefaction occurs where the anchoring element comes intocontact with the bone tissue of the wall of the bone opening andpossibly also where the anchoring element comes into contact with theinner surface of groove 30. Groove 30 may comprise a rough or otherwisesuitably structured inner surface such that liquefaction andre-solidification of the anchoring material may result in a positive-fitconnection not only with the bone tissue of the bone wall, but at thesame time also with the fastener surface inside groove 30.

If a fastener 3 according to FIG. 6 comprises more than one groove,anchoring of the fastener necessitates more than one anchoring step,wherein these anchoring steps may be executed in succession using oneand the same anchoring tool for all the steps, or wherein the anchoringsteps may be executed simultaneously using a fork-shaped anchoring tool.

FIG. 7 is an axial section through a further embodiment of a set offastener 3, anchoring element 6, and anchoring tool 13, which setfurther comprises a guide tool 14 and is suitable for an anchoringprocess similar to the one described in connection with FIG. 6 . The setis illustrated with the fastener 3 press-fitted together with a graft 1in a bone opening 2, the set being ready for the anchoring step. Theguide tool 14 comprises an axial through bore having a cross sectionadapted to the cross section of the anchoring element 6 and to thedistal end of the anchoring tool 13, wherein the through bore is angledrelative to a tool axis by an acute angle of 2 to 10°, preferably 3°. Asalready illustrated in FIG. 6 , for the anchoring step, the anchoringelement 6 is to be advanced from the proximal fastener face along agroove 30 provided on the fastener side opposite the graft 1. Other thanshown in FIG. 6 , the groove 30 according to FIG. 7 comprises a widerentrance portion 30.1 and a narrower distal portion 30.2, wherein thedistal portion preferably has a closed end. In preparation of theanchoring step, the guide tool 31, which may also serve for forcing thefastener into the bone opening 2, is positioned on the proximal fastenerface with the distal mouth of its through bore being aligned with theentrance portion of groove 30. The anchoring element 6 and the distalend of the anchoring tool 13 are positioned in the through bore of theguide tool 31, the distal end of the anchoring element being supportedin the entrance portion 30.1 of groove 30. During the anchoring processthe anchoring element 6 is advanced into groove 30, wherein the angledposition of the anchoring element 6 as illustrated in FIG. 7 as comparedwith the axial position as shown in FIG. 6 forces the material of theanchoring element more against the wall of the bone opening andtherewith enhances liquefaction and penetration into the bone tissue.This effect is amplified by the groove 30 having a closed end.

Experiments show, that anchoring a fastener having a diameter of 8 mmand a distal groove portion 30.2 of a semicircular cross section of 1.5to 2 mm radius using a pin-shaped anchoring element of 3.5 mm diametergives good results.

FIG. 8 is an axial section through a further embodiment of a set offastener 3, anchoring element 6, and anchoring tool 13, the fastener 3and a graft 1 being shown press-fitted in a bone tunnel before theanchoring step. The anchoring element 6 is constituted by an integratedcentral part of the fastener 3 which is e.g. fully made of theliquefiable material, wherein this material may comprise fillercompounds (whiskers, fibers, particles) whose concentration may decreasein a direction from the circumferential fastener surface towards thecentral fastener region constituting the anchoring element 6. Thefastener comprises an inner cavity 4 in the form of an axial channel andat least one passage 5 connecting the channel with an anchoring sectorof the circumferential fastener surface. The channel preferably has awider proximal portion 32 and a narrower distal portion 33, and theanchoring tool 13 adapted to the fastener 3 has at least a distalportion which is adapted to the wider channel portion 32 for beingguided therein. The anchoring element 6 is constituted by the fastenerportion surrounding the distal (narrower) channel portion 33 and isadvanced and liquefied by forcing the anchoring tool 13 from the widerchannel portion 32 into the narrower channel portion thereby pressingthe liquefied material through the passages 5 to the outer fastenersurface. Further embodiments and details of the fastener and anchoringprocess as illustrated in FIG. 8 are described in the publicationUS-2008/262517 (Stryker Trauma GmbH), whose disclosure in its entiretyis enclosed herein by reference.

FIG. 9A is an axial section through a further embodiment of a setcomprising a fastener 3, an anchoring element 6 and an anchoring tool13, wherein the fastener 3 is shown press-fitted with a graft 1 in abone opening 2, on the left hand side of the figure before the anchoringstep and on the right hand side of the figure after the anchoring step.The embodiment may be considered to be a combination of the embodimentaccording to FIGS. 6 and 8 , i.e. to comprise at least one anchoringelement 6 integrated in the fastener 3 which may fully consist of theanchoring material, and which possibly contains a filler having possiblya lower concentration where the material is to be liquefied than inother areas, as discussed in connection with FIG. 8 . However, otherthan shown in FIG. 8 the anchoring element 6 or the material to beliquefied respectively is not situated in a central area of the fastenerbut at the circumferential surface thereof, as discussed in connectionwith FIG. 6 . The anchoring tool 13, which preferably has a taperingdistal end, is forced into the fastener material parallel to the wall ofthe bone opening in the surface region of the liquefiable material. Whenafter completion of the anchoring step the anchoring tool is removed, itleaves a void 15′ between a central area of the fastener and theanchorage 15 in the bone wall, which is connected to the rest of thefastener beside the void 15′ as clearly seen in FIG. 9B (cross sectionthrough the anchored fastener 3).

FIGS. 10 to 17 show various embodiments of fasteners 3 based on thefastener principle (fastener with inner cavity 4 connected tocircumferential fastener surface and anchoring element adapted to fitinto the inner fastener cavity) as illustrated in FIGS. 1 to 5 butdiffering in form. All these fasteners 3 are applicable in the fixationmethods and applications as illustrated in FIGS. 1 to 5 .

FIG. 10 is a three-dimensional illustration of a very simple fastener 3which has the form of a circular cylinder with a rounded distal end. Itcomprises an inner cavity 4 and one only slot-shaped passage 5connecting the inner cavity 4 with the circumferential fastener surface.

FIGS. 11 to 13 are three-dimensional illustrations of further fasteners3 similar to the fastener of FIG. 10 . These fasteners comprise on theright side (anchoring sector of the circumferential fastener surface)passages 5 connecting the circumferential fastener surface with theinner cavity 4. The passages are in FIGS. 11 and 13 two axiallyextending rows of bores (one row visible), in FIG. 12 one axiallyextending row of substantially circumferentially extending slots. Thefasteners of FIGS. 11 to 13 further comprise on the left side (pressingsector 34 of the circumferential fastener surface) a flattened orconcave sector forming a shallow groove for accommodating the graft tobe fastened. In addition, the fastener of FIG. 13 comprises an axiallyextending ridge 35 in the center of the pressing sector 34 which ridgeserves for holding a folded graft (not shown) which is folded over thedistal end of the ridge 35 for being forced into the bone openingtogether with the fastener 3 in a way similar to the one discussed inconnection with FIG. 4 .

FIG. 14 is an axial section of a further fastener 3 the fastener beingillustrated press-fitted with a graft 1 in a bone opening and the figurefurther illustrating the anchoring element 6, the anchoring tool 13 anda guide tool 14 similar to the guide tool as discussed in connectionwith FIG. 7 , the whole set being ready for the anchoring step. Thefastener 3 comprises at least one channel 4/5 (combination of innercavity 4 and passage 5) extending at an angle to the fastener axis. Theat least one channel 4/5 comprises a first mouth in the proximalfastener face which serves for introduction of the anchoring element 6and possibly a distal end of the anchoring tool and a second mouth inthe circumferential surface of the fastener, which serves for pressingthe anchoring material against the bone wall of the bone opening,wherein the anchoring material is either liquefied within the channel4/5, which for this purpose preferably comprises inner energy directors,or at the interface with the bone wall.

FIG. 15 is an axial section of a further fastener embodiment whichcomprises an inner cavity 4 and a passage 5 wherein the inner cavity 4is arranged non-coaxial with the fastener axis and comprises a step 4′or a corresponding bend which is able to divert the anchoring element 6towards the passage 5. This arrangement results in an effect of forcingthe anchoring material towards the fastener surface or the bone wallrespectively in a similar way as discussed in connection with FIG. 7 .

FIG. 16 is a lateral view of a further fastener 3 comprising an innercavity 4 and passages 5 connecting the inner cavity with thecircumferential fastener surface. The fastener comprises distal andproximal end regions having a greater cross section than a middleregion. The two end regions are in particular spherical. Experimentsshow that the fastener according to FIG. 16 provides a press-fit as goodas a cylindrical fastener but can be introduced into the bone openingwith less force.

FIG. 17 is a three dimensional illustration of a distal end of afastener 3, which is advantageous for being introduced into the boneopening beside a graft, wherein the graft is positioned at the one sideof the fastener 3 which is in FIG. 17 the left hand side of thefastener. The distal fastener end is tapering on this graft side forpreventing graft damage on introduction of the fastener beside the graftin the bone opening. The distal fastener end is tapering on thenon-graft side (right hand side in FIG. 17 ) also but less, wherein thedistal mouth of an axial through bore through the fastener foraccommodation of a guide wire is situated in there. As already mentionedin connection with FIG. 1 , it is advantageous to position the throughbore 37 and therewith the guide wire ex-centrically and as close aspossible to the anchoring side of the fastener. The through bore 37 or aproximal section thereof may or may not serve as inner cavity 4 asdescribed for the fastener embodiments according to e.g. FIG. 1 or 5 .

FIGS. 18 to 22 illustrate ways in which in a fixation according to theinvention the fastener 3 can be adapted to the graft 1 and the boneopening 2. The illustrated fasteners are all suitable for extra-graftfixation and are partly based on the fastener principle as illustratedin to FIGS. 1 to 5 (fastener with inner cavity and at least one passageconnecting the cavity to the circumferential fastener surface andanchoring element adapted to be positioned in the inner cavity), andpartly on the fastener principle as illustrated in FIGS. 6 and 7(fastener with at least one surface groove running in axial directionand anchoring element adapted to be advanced in the groove). Adaptationto the fastener principles according to FIGS. 8 and 9 (anchoring elementintegrated in fastener and anchoring material forced from the fastenerby forcing the anchoring tool into the fastener) can be easily envisagedby one skilled in the art knowing the present disclosure withoutdeparture from the invention.

FIG. 18 is a cross section through the fixated fastener 3 and graft 1,wherein the fastener 3 has a substantially round cross section smallerthan the also substantially circular cross section of the opening. Thegraft 1 which needs to be easily compressible is compacted in a narrowslot between the wall of the opening and the circumferential surface ofthe fastener 3 opposite the anchorage 15 of the fastener in this wall.Exemplary dimensions for the fastener 3, graft 1 and bone openingaccording to FIG. 18 are: opening diameter of 8 mm, fastener diameter 7mm, graft (e.g. with stitched end) sized to easily pass through a 7 mmbore.

FIG. 19 is a top view of a fastener 3 comprising an at least partlyconcave pressing sector 34 forming a very shallow, axially extendinggroove for accommodating the graft. The anchoring sector of the fastener3 (opposite the pressing sector 34) is substantially circular and hasthe same radius as the bone opening 2 provided for the fastener. Thefastener 3 may further comprise an axial through bore 37 adapted to beused for advancing the fastener along a guide wire and/or for threadingsuture ends protruding from a stitched graft end portion through thefastener as above discussed in connection with FIGS. 4 and 17 .Exemplary dimensions for the fastener 3 according to FIG. 19 and a graftand bone opening adapted therewith are e.g.: opening diameter 8 mm,radius of anchoring sector of fastener: 4 mm, area ratio of crosssections of fastener and opening: the same as for the fastener of FIG.18 , graft (e.g. with stitched end): sized to easily pass through a 7 mmbore.

FIG. 20 is a cross section through a fastener 3 and a graft 1 anchoredin a bone opening 2. The fastener comprises a flattened pressing sector34 as discussed in connection with FIGS. 11 to 13 wherein the graft 1 iscompressed in the gap between this pressing sector 34 and the wall ofthe opening and wherein the exact form of the pressing sector 34 isadapted to the form of the graft and to its compressibility.

In FIG. 21 , the fastener 3 has again a substantially circular crosssection which is considerably smaller than the also substantiallycircular cross section of the opening 2. The circumferential surface ofthe fastener 3 is pressed into the graft 1 which is not very deformable,while on both sides of the fastener 3 and possibly of the graft 1 thebone opening 2 remains empty, unless means are provided on the fastener3 for liquefied anchoring material of the anchoring element to flow intothis empty space in addition to the penetration of the bone wall of theopening.

In FIG. 22 the graft 1 is only little compressible and deformable andhas e.g. a substantially circular cross section. A shallow groove(pressing sector 34) is provided in the fastener for accommodating thegraft 1.

FIGS. 18 to 20 are rather theoretical as they ignore the fact that inreality the bone tissue around the bone opening is compressed by theforces acting on the latter on introduction of the fastener and by thepress-fit achieved through this introduction such that the cross sectionof the bone opening is deformed, the degree of this deformation beingdependent of the mechanical properties of the bone tissue.

FIG. 23 illustrates an embodiment of the method according to theinvention in which the opening 2 in the bone is pretreated with a firstportion of liquefiable material to be liquefied in situ and made topenetrate the trabecular structure of the wall of the opening 2 and/orcavities provided therein and, on re-solidification to form a sort ofcomposite layer 40 in which the liquefiable material and the bone tissueare connected to each other in a positive fit connection. Preferablythis pretreatment step is carried out such that the cross section of theopening 2 remains substantially unchanged. Following the pretreatmentstep, the fixation is carried out exactly as described for e.g. themethod as illustrated in FIG. 1 or 5 , wherein, in the anchoring step asecond portion of liquefiable material comprised by the anchoringelement is liquefied in situ and made to get into contact with the firstportion and therewith to be welded thereto. The first and secondportions of liquefiable material preferably comprise the same materialhaving thermoplastic properties but may also comprise different suchmaterials which however need to be chosen to be capable of forming awelded connection 41 under the conditions of the anchoring step.Adaptation of the method illustrated in FIG. 23 to other fastenerprinciples as illustrated in FIGS. 5 to 9 is easily possible for oneskilled in the art and in knowledge of the present disclosure withoutdeparture from the scope of the invention.

The pretreatment step is e.g. carried out in the same way as describedfor the anchoring step of the method according to FIG. 5 wherein nofastener is positioned in the bone opening 2 and the cross sections ofthe foot piece and the anchoring element are only very slightly smallerthan the cross section of the bone opening. Further exemplary methodsfor carrying out the pretreatment step are described in the publicationWO 2009/141252 (Nexilis) and WO-2010/045751, the entire disclosure ofboth being enclosed herein by reference.

For not impairing bone tissue regenertation between the graft and thebone tissue of the wall of the bone opening, it may be advantageous torestrict the above described pre-treatment to the anchoring side of thefastener. Such selective pretreatment of the wall of a bone opening isdescribed in the above mentioned publication WO-2010/045751 inconnection with FIG. 8 .

FIG. 24 illustrates an exemplary embodiment of an expandable fastenerwhich is suitable for an extra-graft fixation and an anchoring step asdescribed for the method as illustrated in FIGS. 1 to 5 . The fastenercomprises a slotted sleeve part 3 a and a spreader part 3 b, which ise.g. screw-shaped. The sleeve part 3 a is open at least proximally andcomprises at least one axial slot 43 or a plurality of such slots whichare arranged facing one only side of the sleeve part 3 a (anchoringsector). The spreader part 3 b comprises an axial channel 44 andpassages 45 connecting the axial channel 44 with the circumferentialsurface of the spreader part 3 b. The spreader part 3 b is adapted tothe sleeve part 3 a such that on introduction of the spreader part 3 binto the sleeve part 3 a the sleeve part is radially expanded and theslot(s) 43 are opened or widened. The opening provided in the bone isadapted to the sleeve part 3 a such that the latter can be introducedinto the opening after or together with the graft without the need of asubstantial force and such that introducing the spreader part 3 b intothe positioned sleeve part causes enough expansion of the sleeve partfor achieving a sufficient press-fit. The press-fit is produced bypositioning the sleeve part 3 a between the bone wall of the opening andthe graft with the slot(s) 43 facing the bone wall and by then screwingthe spreader part 3 b into the sleeve part 3 a. The anchoring step iscarried out e.g. as described further above in connection with FIGS. 1to 5 wherein the liquefiable material is liquefied in the axial channel44 of the spreader part 3 b and made to flow through the passages 45 andthe slots 43 to get into contact with the wall of the opening. As thereare slots 43 only in an anchoring sector of the sleeve part, thespreader part 3 b may comprise passages 45 all round, wherein suchpassages eventually positioned in the pressing sector will be keptclosed by the sleeve part.

One skilled in the art knows other embodiments of expandable fastenerswhich he can adapt easily to be suitable for the method according to theinvention as illustrated in any one of the FIGS. 1 to 9 or 23 .

FIG. 25 illustrates a further embodiment of the method according to theinvention in which a graft 1 is fastened in a bone opening 2(extra-graft fixation in e.g. a bone tunnel). The left hand side of FIG.25 shows the fastener 3 and the graft 1 press-fitted in the tunnel(assumed introduction direction from the top of the drawing) with theanchoring element 6 ready for the anchoring process (e.g. rigidly fixedto the anchoring tool 13) and on the right hand side the press-fittedand anchored fastener 3, i.e. the finished fixation. The fastener 3 usedin this method comprises again pressing surface portions and anchoringsurface portions, wherein the different portions are arranged along thefastener axis (not like in the previous Figs. sectors arranged aroundthe fastener circumference). In other words, the pressing surfaceportion extends all around the fastener with the anchoring surfaceportion arranged proximally and possibly also distally thereof. Thefastener 3 may have an even proximal face but preferably has a slopingor stepped proximal face oriented to leave more of the bone wall freethan of the graft surface, wherein selected portions of the proximalfastener face may be rough or otherwise suitably structured. Theanchoring element 6 has a cross section which may be substantially thesame as the cross section of the fastener 3 and is pushed into the spacebetween the bone wall of the opening and the graft 1 towards theproximal fastener face and at the same time the anchoring tool 13 isvibrated (or activated for transmitting other energy to the anchoringelement). Therewith the liquefiable material is liquefied at least wherein contact with the bone wall of the tunnel but preferably also where incontact with the proximal face of the fastener 3 and will therewithprovide a proximal anchorage for the fastener 3 in the bone wall. Therewill be no or hardly any liquefaction of the liquefiable material whereit is in contact with the graft, as the graft, contrary to the bone wallof the opening, is mostly soft and cannot provide energy directors forinitiating such liquefaction.

For fully preventing friction and transfer of thermal energy between theanchoring element 6 and the graft 1 it may be advantageous to use in themethod as illustrated in FIG. 25 , an anchoring element 6 andadvantageously an anchoring tool 13 of a cross section which correspondsto only a part of the fastener cross section (e.g. semi-circular crosssection for anchoring element and anchoring tool and substantiallycircular fastener cross section) and to introduce the anchoring element6 into the bone opening 2 beside the graft such that anchoring element 6and graft 1 do not touch or at least not press against each other.

If desired, the distal anchorage using anchoring element 6.1 is effectedin exactly the same way as the proximal anchorage.

As detailed further above, it is advantageous to advance the anchoringelement in the same direction as the fastener 3 was forced into thetunnel for making sure that the anchoring process can in no way weakenthe press-fit achieved by forcing the fastener into the tunnel.Therefore, if distal anchoring is desired too, it will be advantageousto first effect the proximal anchorage (anchoring element 6) and thenthe distal anchorage (anchoring element 6.1).

The anchoring elements 6 and 6.1 may, as above described, have asubstantially similar cross section as the fastener 3. However, this isnot a necessity. The anchoring elements may e.g. further comprisegrooving edges extending axially or reaming structures for grooving orreaming the walls of the opening while the anchoring element is advancedinto the opening. Furthermore, the opening may be provided to be e.g.wider in the area in which the anchoring element is to be positionedthan in the area in which the fastener is to be positioned.

FIG. 26 illustrates fixation (extra-graft fixation) of the end of agraft 1 in a blind opening with the aid of a fastener 3 comprising aproximal surface portion equipped for pressing and a distal surfaceportion equipped for anchoring. The principle of the anchoring processis the same as illustrated in FIGS. 1 to 4 with the difference that thefastener 3 is forced into the opening 2 preferably beyond the end of thegraft to substantially get into contact with the bottom wall of theopening 2. The fastener 3 is then anchored laterally (anchorages 15L)and/or distally (anchorage 15D).

FIGS. 27 to 36 illustrate intra-graft fixations according to theinvention. The principle of such intra-graft fixation is the same asabove discussed for extra-graft fixation which means in particular thatall anchoring principles described above for extra-graft fixation areapplicable also for intra-graft fixation independent on whether they arespecifically discussed below or not.

FIGS. 27 to 29 are cross sections through fasteners 3 applicable forintra-graft fixation in a bone opening being a tunnel with a constant ornon-constant cross section or being a blind bore. The fastenersaccording to FIGS. 27 and 28 are applicable for grafts with two strands(or four strands separated in two pairs) and therefore comprise twopressing sectors 34, which are preferably situated on opposite fastenersides. A distal end of these fasteners is preferably equipped with atransverse groove for accommodation of the graft end at which the graftis e.g. folded. The fasteners according to FIGS. 27 and 28 are anchoredin the wall of a bone opening with the aid of an anchoring element whichis introduced in an inner fastener cavity 4, the liquefied materialbeing forced through passage(s) 5 against the bone wall, whereinaccording to FIG. 27 passage(s) 5 are arranged on one fastener side only(one anchoring sectors only), according to FIG. 28 on opposite fastenersides (two opposite anchoring sectors). The fastener according to FIG.27 further comprises an axial through bore 37 adapted for use of a guidewire and/or for threading a part of suture ends protruding from stitchedgraft ends through it as discussed in connection with FIG. 4 .

FIG. 29 illustrates the same fastener principle as FIGS. 27 and 28 butis applicable for a four-strand graft, the four strands being separatedfrom each other and accommodated in four pressing sectors 34, which arearranged around the fastener 3 e.g. in a regular pattern, mouths ofpassages 5 (anchoring sectors) being arranged between the pressingsectors 34. The fastener 3 according to FIG. 29 is preferably used for agraft comprising two folded strands and comprises at its distal endpreferably two crosswise arranged transversal grooves each one foraccommodating one of the two stand folds.

FIGS. 30 to 33 are three-dimensional illustrations of fasteners having across section similar to the one shown in FIG. 27 or 28 . Thesefasteners differ from each other and from the fasteners illustrated inFIGS. 27 and 28 in the design of the pressing sectors, which accordingto FIG. 30 comprise retention means in the form of transversal ribs 38,while according to FIGS. 31 to 33 the fastener surface of the pressingsectors is substantially smooth. The shallow grooves constituting thepressing sectors 34 have a constant cross section along the fastenerlength for the fasteners 3 of FIGS. 30 and 31 and they have a decreasingdepth and width towards the distal fastener end for the fastener of FIG.32 and towards the proximal fastener end for the fastener of FIG. 33 .Comparative experiments with the fasteners according to FIGS. 30 to 33show that the fastener according to FIG. 31 achieves the best press-fit.

FIGS. 34A and 34B illustrate a set of fastener 3, anchoring elements 6and anchoring tools 13 which are suitable for an intra-graft fixation ofa graft 1 comprising two strands (or more than two strands separated ina pair of strand groups) in a bone tunnel or blind opening, inparticular fixation of a graft 1 which is folded over the fastener 3 andis forced into the tunnel or blind opening together with the fastener 3.The fixation achieved with the set as illustrated in FIGS. 34A and 34Bis based on the anchoring principle as illustrated in FIG. 6 or 7 .

FIG. 34A is an axial section through the complete set before fixation,FIG. 34B comprises two cross sections through the fastener 3 and thegraft 1 before fixation (above) and when the fixation is completed(below).

The fastener 3 according to FIGS. 34A and 34B comprises two surfacesectors equipped for pressing and two surface sectors equipped foranchoring, the different sectors alternating around the fastenercircumference. The pressing sectors 34 comprise shallow axial grooveswhich may end distally in a distal transversal groove 52 in which thefolded end of the graft is accommodated. The anchoring sectors areequipped like the anchoring sector of the fastener according to FIG. 6or 7 . The fastening process for the fastener is substantially the sameas the one described in detail in connection with FIGS. 6 and 7 andtherefore reference is made to the corresponding part of the descriptionfurther above.

FIGS. 35A and 35B show an intra-graft fixation for fastening adouble-strand graft in a bone opening 2 (tunnel or blind opening), thefixation including a proximal anchorage similar to the proximalanchorage shown in FIG. 25 for an extra-graft fixation. FIG. 35A showsthe process in an axially sectioned bone opening, FIG. 35B in a crosssection through the anchoring element 6, wherein in both Figs. the lefthand side shows the situation before the proximal anchorage is effectedand the right hand side shows the finished fixation. The fastener 3 ispress-fitted and possibly laterally anchored in the circumferential wallof the opening 2 (lateral anchorage 15L) using any of the methods asillustrated in previous Figs. Then the proximal anchoring element 6which has a similar cross section as the fastener 3 and may have theform of a frustum is advanced into the opening 2 and pressed against theproximal face of the fastener using a suitably adapted anchoring tool13, therewith achieving anchorage in the wall of the bone opening 2proximal to the fastener 3 and possibly also in the proximal fastenerface. As discussed further above in connection with FIG. 25 , it ispossible to effect a similar anchorage (not shown) on the distalfastener side once the proximal anchorage is made and prevents weakeningof the press fit through the force necessary for advancing the distalanchoring element using a force which has a direction opposite to thedirection of the force used for effecting the press-fit.

All fasteners illustrated in the FIGS. 1 to 34 are substantiallycylindrical or slightly conical and imply to have substantially circularcross sections (not regarding grooves provided in the anchoring sectorsof the fastener surface for guiding an anchoring element and flat orconcave forms in the pressing sectors 34 provided for retaining the softtissue or graft strands to be fastened). Although this will be the mostpreferred fastener form as it is suitable for being introduced in adrilled opening having a simple cylindrical form, this is not acondition for the invention. All the fasteners may have any crosssection (e.g. oval, rectangular, polygonal) and fit into an opening of acorresponding cross section and they may taper continuously or stepwisetowards the distal end and fit in a continuously or step-wise taperingopening.

FIG. 36 illustrates an example of intra-graft fixation (cross sectionthrough anchored fastener 3 and double strand graft 1) in a non circularbone opening using a fastener 3 having a non circular cross section.Therein the bone opening is e.g. provided by punching and has anelongated cross section and of two graft strands one is press-fitted inone end of the elongated cross section of the opening, the other strandin the other end, the fastener 3 being positioned and anchored(anchorage 15) in the center of the elongated cross section. The crosssection of the opening may be e.g. oval or rectangular (with roundededges) and it may be curved as illustrated, or substantially straight,in particular it may be adapted to the anatomical characteristics of thefixation site. The fixation as illustrated in FIG. 36 is e.g. applicablefor ACL surgery and allows very good reconstruction of the naturalsituation regarding the foot print of the fixation, which allowsadaptation to specific anatomical situations and crossing of the twostrands within the knee joint as in the natural joint. While accordingto the state of the art, the elongated foot print can only be achievedwith fixation in two separate bores, which require a minimal distancefrom each other, the fixation according to FIG. 36 can be realized in aconsiderably smaller space and is therefore e.g. easily possible in theknee of a female patient.

FIGS. 37, 38A/B and 39A/B/C illustrate further sets of fastener 3,anchoring element 6, anchoring tool 13 and guide tool 14, wherein theguide tool 14 is suitable not only for guiding the anchoring tool 13 andpossibly the anchoring element 6 during the anchoring progress, but alsofor forcing the fastener into the bone opening preferably along a guidewire 60 for establishing the press-fit of graft 1 and anchor 3 in thebone opening 2. The illustrated sets are suitable for extra-graftfixation but can easily be adapted for intra-graft fixation.

FIG. 37 shows in axial section a fastener 3 and a graft 1 press-fittedin a bone opening 2, wherein the fastener is suitable for an anchoringprocess as illustrated e.g. in FIG. 1 or FIG. 5 . Also shown is a guidewire 60 and a guide tool 14, the guide wire 60 extending through theinner cavity 4 of the fastener, which inner cavity 4 for this purposecomprises a distal end portion and mouth with a cross section adapted tothe cross section of the guide wire 60. The inner cavity 4 is e.g.eccentrically positioned on the anchoring side of the fastener 3, whichfacilitates introduction of the fastener in the bone opening along theguide wire 60. The guide tool 14 is shaped e.g. for manipulation by handand it comprises a distal end with a cross section adapted to theproximal cross section of the fastener 3, i.e. the guide tool 14comprises an axial through bore adapted to continue the inner cavity 4of the fastener in a proximal direction and it further comprises meansfor holding the fastener preferably with a push-on connection, e.g.protrusion 62, which fits into a corresponding depression of thefastener 3. The set further comprises an anchoring element 6 which ispin-shaped and adapted to be introduced through the axial bore of theguide tool 14 into the inner cavity 4 of the fastener 3, and ananchoring tool 13, whose distal end portion is also adapted to beintroduced through the axial bore of the guide tool 14. Anchoringelement and anchoring tool are not shown in FIG. 37 .

Using the set according to FIG. 37 , the fixation process comprises thefollowing steps: introducing the graft 1 and the guide wire 60 into thebone opening; attaching the fastener 3 to the guide tool 14; introducingthe proximal end of the guide wire 60 into the distal mouth of the innercavity 4 and forcing the fastener 3 along the guide wire 60 into theopening, by e.g. using an impaction tool being applied to the proximalend of the guide tool 14 or possibly, for protecting the proximal end ofthe guide wire 60, being applied to a cannulated interface piece 63positioned on the proximal face of the guide tool 14; removing theinterface piece 63 and the guide wire 60; introducing the anchoringelement 6 and the anchoring tool 13 through the axial bore of the guidetool 14 towards the fastener; transmitting energy through the anchoringtool 13 to the anchoring element 6 for the anchoring process; stoppingthe energy transmission and removing the anchoring tool 13 and the guidetool 14.

If the fastener 3 comprises a separate axial bore for the guide wire, asshown e.g. in FIGS. 19 and 27 , the guide wire may be left in this boreduring the anchoring step and may be removed together with the anchoringtool and the guide tool. In such a case it is possible also for theinner cavity to be angled relative to the through bore for the guidewire for an anchoring process similar to the one illustrated in FIG. 14.

FIGS. 38A and 38B illustrate a further set comprising a fastener 3, ananchoring element 6, an anchoring tool 13, and a guide tool 13 in anaxial section (FIG. 38A) and a cross section (FIG. 38B), wherein theanchor is press-fitted together with a graft 1 in a bone opening 2 andthe set is ready for the anchoring step. The set is suitable forintroduction of the fastener 3 into the bone opening 2 along a guidewire 60 and for anchoring the fastener 3 using a method similar to theone illustrated in FIG. 25 . The fastener 3 comprises an anchoringelement 6, which is attached on the proximal face of the fastener andhas a cross section constituting a part of the fastener cross section,e.g. substantially semicircular cross section of anchoring element 6 andsubstantially circular cross section of fastener 3. The fastener 3 andthe anchoring element are preferably made as one piece and consisting ofthe same thermoplastic material At the transition from the anchoringelement 6 to the fastener 3, the anchoring element comprises a reducedcross section, e.g. through a groove 70 running along thecircumferential surface between anchoring element 6 and fastener 3. Thecross section reduction serves for concentrating the vibration energytransmitted by the anchoring tool to the anchoring element 6 such thatliquefaction of the anchoring element starts in the region of the crosssection reduction, i.e. on the distal side of the anchoring element oron the proximal face of the fastener respectively. The fastener 3 andpossibly the anchoring element 6 further comprise an axial through borefor accommodation of the guide wire 60.

The cross section of the anchoring tool 13 is adapted to the crosssection of the anchoring element 6. The guide tool 14 comprises an axialbore for the guide wire 60 and a channel adapted to the cross section ofthe anchoring element 6 and the anchoring tool 13. The guide tool 14 canbe easier manufactured if it comprises an inner part 14.1 with the borefor the guide wire 60 and with a groove adapted to the anchoring element6, and an outer part 14.2 consisting of a thin tube in which the innerpart 14.1 is fixed and which closes the groove of the inner part toconstitute a channel for the anchoring element 6 and the distal end ofthe anchoring tool 13, and which reaches on the anchoring side (lefthand side in FIG. 38A) into the bone opening and to an axial positionjust proximal of the groove 70 and therewith prevents too proximal exitof the liquefied material of the anchoring element.

Fixation using the set according FIGS. 38A and 38B is carried out in asimilar manner as described for the set according to FIG. 37 , whereinthe guide wire 60 need not be removed before the anchoring step. FIG.38A and B show the set ready for the anchoring step, with the guide wirestill in position.

FIGS. 39A/B/C illustrate a further set of fastener 3, anchoring element6, anchoring tool 13 and guide tool 14, the set being shown in twolateral views (FIG. 39A and 39B turned around the axis by 90° relativeto FIG. 39A) and axially sectioned (FIG. 39C). The set is shownassembled and ready for the anchoring step (guide wire removed, notshown). The set is suitable for anchorage using a method as illustratedin FIG. 1 . The fastener 3 comprises an inner cavity 4 which is adaptedto the anchoring element 6, is connected to the circumferential fastenersurface by passages 5 and may comprise a narrow distal mouth for theguide wire. For being mounted on the guide tool 14 the fastenercomprises a stepped proximal profile 72 and a proximal inner thread.

The guide tool 14 comprises in inner part 14.1 and an outer part 14.2,wherein the two parts are rotatable and axially displaceable relative toeach other. The inner part 14.1 of the guide tool 14 comprises the borefor introduction of the anchoring tool 13 and the anchoring element 6and at its distal end an outer thread adapted to the inner thread of theanchor for a screwed connection 73 between the inner guide tool part14.1 and the fastener 3. The outer guide tool part 14.2 comprises at itsdistal end a stepped profile 72′ fitting into the stepped profile 72 ofthe fastener 3. The proximal end of the inner guide tool portion. 14.1comprises a handle knob 74 positioned within a lantern shaped proximalend portion 75 of the outer guide tool part 14.2 where an operator cangrip it with his fingers for rotating the inner part 14.1 relative tothe outer part 14.2 of the guide tool 14.

For mounting the fastener 3 to the guide tool 14, the fastener 3 ispushed against the distal end of the guide tool 14, the stepped profilesof the fastener 3 and the distal end of the outer guide tool part 14.1meshing. Then the inner guide tool part 14.1 is rotated for its distalend being screwed into the fastener 3 which is prevented from rotationby the meshing stepped profiles 72 and 72′. If a guide wire is used forintroduction of the fastener 3 into the bone opening, the assembled setis then used as described for the set according to FIG. 37 , whereinafter removal of the guide wire, the anchoring element 6 and theanchoring tool 13 are introduced into the axial bore of the guide tool14, wherein the anchoring tool 13 may already be coupled to an energysource (preferably vibration source). For such coupling e.g. the housingof a suitably adapted ultrasonic device is screwed or snapped onto thelantern shaped proximal end portion of the outer guide tool part 14.2,thereby snap-coupling the anchoring tool to the vibration generator. Asuitable ultrasonic device is described e.g. in the patent applicationPCT/CH2010/000279, which is not published yet and whose disclosure isincorporated herein in its entirety by reference.

In the above description and appended figures a plurality of embodimentsof method, fastener, and set according to the invention are disclosedwherein each figure shows a specific combination of features. Oneskilled in the art will easily be capable of transferring in a suitablemanner selected ones of these specific features from one embodiment toanother one without the need of inventiveness and without departing fromthe scope of the invention.

Experimental Results

Extra-graft fixations according to the invention have been realized andcompared with similar fixations effected with the aid of interferencescrews according to the state of the art and effected with the aid offasteners according to the invention but not being anchored in theopening (press-fitting only). Furthermore, these fixations were comparedwith the published data for the simple press-fit dowels as described inthe initially referenced publications by Mayr et al. The comparisonsregarded fixation strength, fixation stiffness, graft migration underlow cycle fatigue conditions (1000 cycles of a frequency of 0.5 Hz) andfinal failure causes.

The fasteners used in the experiments were the fasteners as shown inFIGS. 10 to 13 . These fasteners as well as the interference screws usedfor the comparison had a diameter of 7 mm and a length of 30 mm and weremade of titanium, stainless steel, PEEK or HA-PLA. The anchoringelements were made of PLDLLA. The grafts were four-strand grafts madefrom bovine digital extensor from the forelimb by doubling over of twosized tendons, the final graft to pass easily through a bore of 7.5 mmdiameter. The bone openings in which the grafts were fastened weretunnels of 8 mm diameter drilled through bovine tibial bone using atibial cortex reamer.

Generally speaking the comparison showed that using the fixationaccording to the invention it is possible to achieve initial pull-outforces which are higher by up to 130%, initial failure forces which arehigher by up to 100%, fixation stiffnesses which are higher by 40% atcomparable graft migration under low cycle fatigue conditions and,compared with interference screw, less graft damage.

What is claimed is:
 1. A set for fastening tissue or a prostheticelement in an opening provided in a human or animal bone, the setcomprises a fastener, the fastener comprising a proximal face, a distalend, a fastener axis extending between the proximal face and the distalend and a circumferential surface extending around the fastener axis,and the fastener further comprising at least one first portion of thecircumferential surface and at least one second portion different fromthe first portion of the circumferential surface, the set furthercomprising at least one anchoring element, wherein the anchoring elementcomprises a liquefiable material strengthened by admixed fibers orwhiskers, the anchoring element is adapted to axially extending groovesin the circumferential surface, to channels extending at an angle to thefastener axis from the proximal fastener face to the circumferentialsurface, or to an inner cavity of the fastener or is integrated in acentral or peripheral fastener region, and wherein the at least onefirst portion is equipped for anchoring by comprising means for guidingthe liquefiable material to the first portion or along the firstportion, or by comprising the liquefiable material.
 2. The set accordingto claim 1, wherein the fibers or whiskers are made of or comprisedegradable materials.
 3. The set according to claim 1, wherein thefibers or whiskers comprises calcium phosphate ceramics or glasses orare made of calcium phosphate ceramics or glasses.
 4. The set accordingto claim 1, wherein the anchoring element comprises a composite materialor is made from a composite material.
 5. The set according to claim 1,wherein the fastener is made of a calcium phosphate.
 6. The setaccording to claim 1, wherein the fastener is fully made of theliquefiable material strengthened by admixed fibers or whiskers whoseconcentration decrease in a direction from the circumferential fastenersurface towards the central fastener region constituting the anchoringelement.
 7. The set according to claim 1, wherein the fastener issuitable for fixation of a stitched graft end or a stitched tissue endin a bone opening being a blind bore, wherein the stitched graft endcomprises a first suture end and a second suture end wherein and whereinthe fixation of the stitched graft end or the stitched tissue end to thefastener can be achieved by threading the first suture end through aninner cavity of the fastener, which for this purpose comprises an opendistal end, and the second suture end along the circumferential surfaceof the fastener.
 8. The set according to claim 7, wherein the firstsuture end and the second suture end can be connected by a knot or othersuitable suture retainer at the proximal fastener face.
 9. The setaccording to claim 7, wherein the circumferential fastener surface orthe inner fastener cavity comprises an axially extending groove foraccommodation of the first suture end or respectively the second sutureend.
 10. The set according to claim 9, wherein the circumferentialfastener surface comprises an axially extending groove for accommodationof the first suture end and the inner fastener cavity comprises anaxially extending groove for accommodation of the second suture end. 11.The set according to claim 2, wherein the fibers or whiskers comprisescalcium phosphate ceramics or glasses or are made of calcium phosphateceramics or glasses.
 12. The set according to claim 2, wherein theanchoring element comprises a composite material or is made from acomposite material.